This invention pertains to thermosettable compositions containing a compound which simultaneously contains both a maleimide group and a cyanate group and a polyamine.
Aromatic polycyanates which are thermosettable to polytriazines are known, for example, from U.S. Pat. Nos. 3,448,079; 3,553,244; 3,694,410; 3,740,348; 3,755,402; 4,094,852 and 4,097,455. Said polytriazines possess excellent heat resistance, however, their mechanical properties, especially tensile strength and elongation are deficient. Furthermore, there is substantial room for improvement in the reactivity of said polycyanates both in homopolymerizations and copolymerizations.
Copolymerization products of compounds containing two or more maleimide groups with compounds containing two or more cyanate groups and compounds containing two or more amino groups are known, for example, from U.S. Pat. Nos. 4,110,364; 4,371,689 and 4,396,745. Included within their teachings is the use of coprepolymers of bismaleimides and polyamines as well as the use of coprepolymers of aromatic polycyanates and polyamines. Preparation of said copolymerization products always requires premixing or contacting together of three separate components: the polycyanate compound, the polymaleimide compound and the polyamine compound. Furthermore, preparation of the aforesaid coprepolymers of bismaleimides and polyamines or aromatic polycyanates and polyamines is difficult to control and often leads to high molecular weight components which are difficult to use in the further copolymerization reaction due to low solubility and reduced processability.
The present invention alleviates the necessity to mix three separate components while still providing a copolymerizable mixture containing cyanate groups, maleimide groups and amino groups. This is accomplished by mixing a compound which simultaneously contains both a cyanate group and a maleimide group with an aromatic polyamine. As an additional benefit, the aforesaid copolymerizable mixture offers substantially enhanced reactivity over that of the compound which simultaneously contains both a cyanate group and a maleimide group alone.